Apparatus for generating electric energy



Jan 6, 1931.

W. D. FLETCHER APPARATUS FOR GENERATING ELECTRIC ENERGY Filed April 20, 1929 mam Wan

S r FW? INVENTOR ifilliam flF/efe'fier ATTORNEY Patented Jan. 6, 1931 UNITED 's'rA'ras:

PATENT orrlca Application filed April 80,

This'invention relates to a system for the generation of auxiliary electric power from a main prime mover operating at variable speeds. a It is an object of this invention to rovide a system in accordance with whic such power may be generated from the main prime mover efficiently and economically but in accordance with which any changes in speed of the main prime mover are automatically compensated or.

In many installations, such for example, as on board a ship, generators are provided for the generation of the current required, upon the ship. It is desirable to operate these generators from the main prime mover of the ship, as for example by connecting them direct to the main propeller shaft. Such shaft, however, may at difi'erent times 59 operate at widely varying speeds and at times may be reversed in direction.

It is an object of this invention to insure that the generator shall be operated at all times at its predetermined speed regardless of the speed or direction of'the rotation of the main shaft. To accomplish this result there is provided an auxiliary prime mover "in addition to the main prime mover and the two rime movers are differentially connecte to the generator in such a manner that any change in speed of the main prime mover may be compensated for by a change in speed of the auxiliary prime mover. This may convenientl be accomplished by rotating the armature o the enerator by one of the prime movers and the eld by the other. I

bodiment of the invention has therefore been chosen for illustration. e

The figure is an elevation, plartly in section,

of a machine embod 'ng t e invention in which the numeral 1 esignates a frame having journalled therein. a shaft 2 which may be connected to the main rime mover. An auxiliary prime mover in cated at 3 has its shaft 4 also journalled in the frame 1 in alinement with the shaft 2.

A enerator indicated generally at 5 has two eiments 6 and 7'comprising respectively a field and armature. One of these elements,

'' a! for example the field element 6, is mounted This em-- 1929. man He. stem.

The generator chosen for illustration is of the alternatin current'type, the current be ing conducted to the field magnets through suitable sli rings 10 and 11 and the current being with rawn from thearmature through slip rings 12 and 13.

With this construction it will be clear that the current generated will depend upon the difference in speed of the two prime movers. Automatic means are provided for maintaining this difference constant by alteration of the speed of the shaft 4. To accomplish this result there is mounted upon the frame 1 a differential indicated generally at 15 which may assume the form of a housing 16 journaled at 17 and 18 upon the frame 1. A pair of shafts 19 and 20 are journalled in the housing concentric with the journals 17 and 18 and carry at their inner ends within the housingilbevel gears 21 and 22 which mesh in turn wit bevel gears 23 and 24 journalled in the housing 16 on an axis at right angles to the shafts 19 and 20. The shaft 19 carries a pulley 25 which is driven from a pulley 26 upon the shaft 2 by means of a belt 27. The corres onding'shaft 20carries also a pulley 28 which is driven from'a ulley 29 upon the shaft 4 by means of a bel belts, as for example the belt 30, is crossed.

The housing v16 carries a bevel gear 31 meshing with a bevel gear 32 upon a governor shaft 33 journalled in the frame 1 as shown at 34. This shaftdrives a pair of spring arms t 30. One of the 35 each carrying a weight 36, the arms being A rigidly held at their upper ends and bein connected at their lower ends to a block 3 slidable u on the shaft 33. A bell crank lever 38 pivote at 39 to the frame 1 has one of its arms 40 engaging a slot 41 in the block 37 Theother arm 42 of the bell crank lever operates a rod 48 to operate a valve 44 to control the flow of motive fluid to the prime mover 3.

With the above construction it will be clear that the housing 16 will rotate at a s eed which is one half of the sum of the s ee 5 of rotation of the shafts 19 and 20 an this by reason of the crossed belt 30 corresponds to the difference in the speed of rotation of the shafts 2 and 4.

The apparatus may be arranged so that the shaft 4 normall rotates either in the same direction or in t e opposite direction to the shaft 2 when the shaft 2 is oing at its full forward speed but it is simp er to arrange it so that either it does not rotate or it rotates in the opposite direction to the shaft 2 when the latter is going full s eed forward because.

with this arrangement a 1 changes in the speed of rotation or direction of the shaft 2 may be compensated for by chan es in the speed of the shaft 4 without changing its direction of rotation.

The overnor 36 will be arran ed so that normal? when the propeller sha t 2 is being driven orward at customary full speed, the valve 44 will admit steam to the secondary prime mover 3 sufiicient to hold the rotor of the latter stationary against the torque of the field 6 which is carried by said propeller shaft. But little s cam is required to do this since its torque on t e stationary turbine rotor is three or four times the torque that is developed when therotor is rotating at normal speed. As soon as the s eed of shaft 2 begins to fall off, the governor egins to further open the steam inlet so as to maintain the desired constant differential s eed between the field and the armature. S ould the main prime mover stop altogether, the full burden of generation will be taken u by the auxiliary prime mover 3, which Wlll now have correspondingly increased its speed. Should the main shaft be reversed a still further quantity of motive fluid will be admitted to the prime mover 3 and a still higher speed will be required of the shaft 4' but in each instance the relative speed of the generator parts and consequently the voltage'of the generator will be maintained constant.

With the above construction, it will be clear that during normal operation of the main prime mover while it is moving at full speed, it will furnish the power required for the current generation and the advantages of its high e ciency will be secured. At the same time, all speed changes of the main prime mover are fully compensated for in a practical and eflicient manner.

In certain applications of the invention, it may be desirable to design the control so that while shaft 2 is rotating at its normal rate and in its normal direction of rotation, the

secondary prime mover 3 may be either stationary, revolving in the same direction as shaft 2, at a greater rate of speed, or at a lesser rate of speed; or prime mover 3 may be'rotating in one direction and shaft 2 in the opposite direction.

It is understood that the governor 36 and valve 44 are merely diagrammatic, that any desired form of governor may be used and that in actual practice for control of speed of a turbine the valve element would ordinarily operate to cut in and out a greater or less number of steam nozzles operating on the turbine rather than to increase the amount of steam discharged through a single nozzle. In certain cases, the current output of the generator may be used to control the speed of the secondary prime mover 3. In any case, a voltage regulator may be employed to keep up the voltage by increasing the field magnetizing current through a certain range of varying speed of the pro ellershaft 2 and when that range is excee ed, a relay mechanism will operate to co-relatively speed up the secondary prime mover 3. In all cases, the voltage regulator will operate to smooth out imperfections in the governing for the desired constant differential speed of the rime movers.

Since certain changes ma be made in the above construction and different embodi-. ments of the invention could be made withoutdeparting from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limitin sense.

It is also to be un erstood that the following claims are intended to cover all of the eneral and s ecific features of the invention erein descri ed, and all statements of the scope of the invention which, as a matter of Ian uage, might be said to fall therebetween. aving described my invention, what I claim as new and desire to secure by Letters Patent, is

1. In an apparatus for generating auxiliary electric power from a main prime mover, in combination a secondary prime mover, a generator having two rotating ele ments one of which carries the field and one the armature, each said elements bein connected to one of said prime movers, a ifferential responsive to the difference in speed of said elements, and a governor operated by said differential to control the power input to said secondary prime mover to maintain aconstant difference in speed between said elements.

2. In an apparatus for generating auxiliary electric power from a main prime mover, in combination a secondary prime mover, a generator having two rotatin elements one of which carries the field an one the armature, each said elements bein connected to one of said prime movers, a ifl'erential responsive to the difference in speed of said elements, and a governor operated by said difierential to control the efiect of said secondary prime moverupon the rotating element connected thereto, to maintain a constant difference in speed between said elements.

| 3. In an apparatus for generating auxiliary electric power from a main prime mover, in combinatlon a secondary prime moves. a. generator having two rotating elements one of which carries the field and one the armature, each said elements being connected to one of said prime movers, a differential responsive to the difference in speed ofsaid elements, and a governor operated by said difierential to increase thetpower input to said secondary prime mover with each decrease in speed of the main prime mover.

Signed at New York in the county of New York and State of New York this 16th day a of April A. D. 1929.

20 WILLIAM D. FLETCHER. 

